The invention relates to aliphatic polycarbonate homo- and co-polymers which are obtained by ring-opening homo- or co-polymerization of cyclic carbonates by DMC catalysis.
Double metal cyanide (DMC) catalysts useful for the ring-opening polymerization of oxygen-containing, cyclic monomers have been known for a long time. DMC catalysts are of particular commercial interest for the production of polyether polyols by polyaddition of epoxides to starter compounds exhibiting active hydrogen atoms (See, e.g., U.S. Pat. Nos. 3,404,109; 3,829,505; 3,941,849 and 5,158,922.) because the use of a DMC catalyst reduces the proportion of monofunctional polyethers with terminal double bonds (so-called xe2x80x9cmono-olsxe2x80x9d) compared to polyether polyols produced using conventional alkaline catalysts. Moreover, improved, highly active DMC catalysts, which are described, e.g., in U.S. Pat. No. 5,470,813; EP-A 700 949; EP-A 743 093; EP-A 761 708; WO 97/40086; WO 98/16310 and WO 00/47649, possess extraordinarily high activity and permit polyether polyol production at very low catalyst concentrations (25 ppm or less). Consequently, it is no longer necessary to separate the catalyst from the finished product. In addition, DMC catalysts also make possible the home and copolymerization of other oxygen-containing, cyclic monomers, such as oxetanes, (U.S. Pat. No. 3,278,457 and 3,404,109), cyclic anhydrides (U.S. Pat. No. 5,145,883 and 3,538,043) and lactones (U.S. Pat. No. 5,032,671).
Aliphatic polycarbonate homo- and co-polymers are suitable as additives for thermoplastic systems. Moreover, aliphatic, OH-functional polycarbonates are widely used as a hydroxyl component for building up polyurethanes and polyurethane-urea elastomers. Common methods for the production of aliphatic polycarbonates are transesterification of a diol with a dialkyl carbonate from a short-chain alcohol, with a dioxolanone or with a diphenyl carbonate. These reactions are accelerated by catalysts, particularly alkali, tin and titanium compounds (See, e.g., Kunststoffhandbuch, vol. 3/1 Polycarbonate, Hanser Verlag, Munich, 1992, p. 118f.).
It has now been found that aliphatic polycarbonate homo- and co-polymers can be obtained by ring-opening homo- or co-polymerization of a cyclic carbonate by DMC catalysis.